1. Field of the Invention
This invention relates to a method for the production of fluorenone and more particularly to a method for producing fluorenone by the vapor-phase catalytic oxidation of fluorene with a high yield. Fluorenone is a commercially useful substance as raw materials for agricultural pesticides, medicines, and functional macromolecular compounds.
2. Description of the Related Art
The method for producing fluorenone by the vapor-phase catalytic oxidation of fluorene with molecular oxygen is at an advantage in enjoying high productivity as compared with the liquid-phase method and avoiding emission of waste liquor. It is nevertheless at a disadvantage in having to sacrifice selectivity when the reaction is performed at a high conversion. It incurs difficulty in effectively utilizing fluorene while maintaining high productivity. It does not easily produce fluorenone stably with high yield because it entails the phenomenon of suffering the selectivity of fluorenone to be lowered and the catalytic activity to be varied, depending on the quality of the raw material fluorene to be used.
The method for the production of fluorenone is known in two types, the liquid-phase method and the vapor-phase method. As to the liquid-phase method, many reports have been published on the method of liquid-phase oxidation with molecular oxygen by the use of a phase-transfer catalyst formed of an aqueous alkali solution, a hydrophobic organic solvent, and a quaternary ammonium salt (JP-A-07-82,206 and JP-A-07-82,207). As to the vapor-phase method, a method using vanadium pentoxide (U.S. Pat. No. 1,374,695), a method using a catalyst formed of iron vanadate and potassium sulfate (Zh. Pyirl Khim 35, 693-696 (1962)), a method using a catalyst formed of vanadium pentoxide and tin oxide (Engineering Chemical Journal, 56, (6), 413-416 (1953)), a method for causing inclusion of a large volume of water by the use of a catalyst formed of at least one metal element of the fifth and sixth groups of the periodic system (U.S. Pat. No. 1,892,768), a method using a catalyst formed of vanadium pentoxide, silica, and potassium sulfate (U.S. Pat. No. 2,956,065), and a method using a catalyst formed of a vanadium oxide, titania, and an alkali metal compound (JP-A-60-233,028) have been disclosed. In addition to these methods, a method using a catalyst formed of a system of vanadium-iron-cesium (Stud, Surf, Sci. Catal. (1993), 75 (New Frontiers in Catalysis, Pt. A), 707-17) has been also disclosed.
It has been heretofore known that a vanadium-based catalyst can be used as an effective catalyst for the production of fluorenone by the vapor-phase oxidation of fluorene. It has been difficult, however, to obtain fluorenone stably with a high yield because the reaction performed at a high conversion results in lowering the selectivity and the quality of the raw material lowers the selectivity or changes the catalytic activity.
An object of this invention, therefore, is to provide an improved method for the production of fluorenone.
Another object of this invention is to solve the problems heretofore attendant on the vapor-phase oxidation and provide a method for producing fluorenone stably with high selectivity.